1. Field of the Invention
The present invention relates generally to the field of Heterogeneous systems, optimization of the authentication procedure during Inter access system handovers, and a method of key derivation for the evolved system. More particularly, this invention provides a method of deriving new keys for securing communication with the new access system after handover using the previous access system keys.
2. Description of the Related Art
The Radio Access Network (RAN), System Architecture (SA) and the Core Terminal (CT) working groups of the Third Generation Partnership Project (3GPP) aim to develop an Enhanced UTRAN (E-UTRAN) architecture for next generation wireless systems. The E-UTRAN system is required to co-exist with the Second (2G) and Third Generation (3G) wireless systems, and in particular, to support handovers between the existing systems and the newly evolved E-UTRAN system, specified in the 3GPP TR 23.882, 3GPP TS 23.401 and 3GPP TS 23.402 specifications.
The E-UTRAN system is an evolution of the 3GPP UTRAN system, in which the main entities are the User Equipment (UE), the Enhanced Node B (ENB), Mobility Management Entity (MME), User Plane Entity (UPE) and Inter Access System Anchor (IASA) as shown in the FIG. 1. The ENB of the EUTRAN system should have the features of the Node B and the Radio Network Controller (RNC) of the legacy UTRAN system. MME of the System Architecture Evolution (SAE) manages and stores UE context (for idle state: UE/user identities, UE mobility state, user security parameters). The MME also generates temporary identities that it allocates to UEs, checks the authorization as to whether the UE may camp on the TA or on the PLMN (Public Land Mobile Network), and authenticates the user. The UPE of SAE terminates for idle state UEs the downlink data path and triggers/initiates paging when downlink data arrive for the UE. The UPE also manages and stores UE contexts, e.g. parameters of the Internet Protocol (IP) bearer service or network internal routing information, and performs replication of the user traffic in case of interception. IASA is the user plane anchor for mobility between different access systems. It performs or supports handover between different access systems.
The Global System for Mobile Communication (GSM)/Enhanced Data rates for Global Evolution (EDGE) Radio Access Network (GERAN) consists of the Base Transceiver Station (BTS) and the Base Station Controller (BSC). The UTRAN consists of the Node B and the Radio Network Controller (RNC). The General Packet Radio Service (GPRS) Core Network consists of the Serving GPRS Support Node (SGSN) and the Gateway GPRS Support Node (GGSN) as shown in FIG. 1
The Integrated Wireless Local Area Network (I-WLAN) system specified in the 3GPP TS 23.234 specifications provides a system and method to integrate legacy UTRAN systems with WLAN systems, as shown in FIG. 2. The I-WLAN system allows WLAN users to access 3GPP packet switched services.
Currently, however, there is no efficient mechanism specified to provide authentication procedure during handover between the heterogeneous access systems. Also, there is no method described to generate keys for the evolved system.